It is often necessary to implant an endoprosthetic device within the living bone of a patient, e.g. during a hip replacement surgery. In this procedure, the medullary canal within the bone is first reamed as known in the art, and then an endoprosthesis having a long shaft is thrust into the reamed canal to form an interference fit therein.
Unfortunately, this interference fit method of endoprosthetic implantation often results in a poor fit between the prosthesis and surrounding bone tissue, resulting in a gap at the interface between the bone and the prosthesis. What starts as micromotion, typically in the proximal area of the implant, can result in instability of the implant over time. As the implant becomes looser and more unstable within the medullary canal, it moves increasingly back and forth from cyclic loading within the medullary canal, grinding against the surrounding bone tissue. This can result in both mechanical wear and osteoclastic resorption of surrounding bone tissue, further compounding endoprosthetic instability. The short-term result is enhanced pain for the patient, and the ultimate result is a failure of the endoprosthetic implant which must be replaced surgically. However, surgical replacement becomes more difficult with each failure because the prior reaming of the medullary canal and loosening of the implant through osteoclastic resorption greatly reduce the amount and quality of available bone tissue to anchor the implant.
In addition, endoprosthetic implantation has traditionally been limited largely to the elderly population. Therefore, in the past, endoprostheses were not usually required or expected to have useful lives longer than about 10-15 years. However, it is becoming more common to implant endoprostheses in younger patients, for example in young adults 18-50 years of age. It is desirable, especially for younger patients, that endoprostheses have a useful lifespan longer than the traditional 10-15 years, preferably at least 20, 25, or 30 years, or longer. Accordingly, there is a need in the art for a material to fill the gap between an endoprosthetic implant and the surrounding bone tissue in the medullary canal that provides a longer useful life for the implant. Such a material preferably will speed healing of bone tissue in the medullary canal following implantation, and most preferably it will promote bone growth and adhesion toward (preferably to) the implant itself.